1. Field of Invention
The present invention pertains to liquid and gas supply systems for processes requiring gas mixtures, particularly welding operations.
2. Related Art
The use of underwater pipelines to convey products such as natural gas and oil (e.g., between countries or from offshore production facilities to onshore terminals) has been undergoing continuous development over the years. In particular, a number of methods have been developed for fabricating and laying underwater pipelines, including: (1) fabrication of the pipelines on shore, followed by transporting the pipeline lengths to the selected location offshore for underwater installation; and (2) fabrication of the pipelines offshore on a large floating vessel, e.g., a barge, where individual sections of pipe are welded together on the barge and then lowered into position underwater as the barge advances. The barge fabrication/installation method is particularly useful in that smaller pipeline sections are easily stored on the barge and individually manipulated to construct a large, continuous pipeline by welding each individual section to the end of the pipeline.
However, the barge fabrication/installation method suffers from certain drawbacks. In particular, the welding gas used to weld the pipeline sections together, which is typically a mixture of carbon dioxide and argon, is stored on the vessel and used during the pipeline fabrication process. Once this welding gas is depleted, the fabrication process must be halted until a new source of welding gas is supplied. This can take some time, particularly if the barge is a considerable distance from land. The logistics and cost associated with current supply modes can be limiting. In addition, the welding gas storage tanks must be monitored to determine when the welding gas is about to become depleted and to coordinate delivery of a new supply of gas. Further, if a problem occurs with one or more pieces of welding gas supply equipment, the fabrication process must also be halted until such time as new equipment and/or service technicians can be delivered to the vessel to repair any damaged equipment and render the welding gas supply system operational.